PM66 Vibration

[Wayne Jolly]

Hi everyone. I just acquired a PM66 a few weeks ago ( I think it's a 1996 model) and when I started cleaning it up and checking all of the alignments, I found that the saw blades wobble about .006". I assumed it was the arbor and/or arbor bearings so I ordered a new kit from Powermatic and just installed it today. What I found is that I now have a perfectly good spare arbor, the blades still wobble, and the machine has a definite vibration. The new arbor and bearings did not help at all. &^%$.

So now that I have a known good arbor and bearings, what else could cause this amount of run-out. I can think of a lot of things to look into, but all of them would just cause the blade to be out of proper alignment, but not cause .006" runout.

Thanks,

Wayne

P.S. I don't have an alignment plate, but the 4 blades that I have measured all wobble about .006" and all of them run true on the contractors saw that I am replacing.

[Mike Goetzke]

Try measuring the arbor runout but 0.006" doesn't sound excessive. Maybe belts or loose pulley?

Mike

[Don Jarvie]

You may want to give it the once over. Take off the top take off the motor. Make sure the trunions are tight and check to make sure the tilt and blade up and down are smooth. Get a wire brush and clean out all the dirt and saw dust and hit everything with some paste wax.

Make sure the motor is tight and check the motor pulley set screws to make sure there tight. Put the motor back on and line up the pulleys and belts (arbor and motor) so the are pararel to each other then turn it on and see if vibrates. If not put the top back on and give it a go.

You may want to replace the belts. Get a matched set, i.e the belts are numbered in a row.

No one has probably cleaned up the saw in 15 years so thats all it may need. Most likely the belts are old and if they are a hair off they could cause a vibration.

[John McClanahan]

Try taking off all but 1 belt and see if that helps. When I bought my PM66, one of the belts would tighten ahead of the others. The less than tight belts would flop, causing vibration.

[Wayne Jolly]

Thanks for the replies.

When I measured the run-out, I measured it at a point roughly 8" our from the center of the arbor shaft. Or to put it another way, about 1" to about 1 1/2" from the outer edge of the blade.

I have already decided that I am going to disassemble at least some of the saw. I'll take the top off and clean it out and check the things that have been mentioned. I want to take the belts off and start the motor to see if it runs smoothly, then check to make sure the two pulleys are aligned properly and tight. Then I will try putting on just one belt to see if it still runs smoothly. Then I'll try the other belt, and then both again.

As for the belts themselves, they don't "look" very old. They are clean and the "Powermatic" printing is clearly visible. I don't know if they are a matched set or not, but I will see if I can find out. One thing I did notice is that they appear to have a "memory". I can turn the blade by hand (saw unplugged of course), and it will be like pulling it "uphill" for 1/2 of the revolution, then it will run "downhill" by itself for the remainder of the revolution. I let the saw run for a good 10 minutes once to see if it would clear up, but it did not.

I know that .006" run-out at the edge of the blade doesn't seem like a whole lot, but as much as it pains me to say this, my Craftsman contractors saw yields much cleaner cuts with the same blade. That just cannot stand.

Thanks again,

Wayne

[Thomas Hotchkin]

Wayne
Have you checked run out at the arbor? Did you check outer blade washer for being flat, they can cause some problems with the blade. and is it the same size as your arbor flange? Did you mark the blade were the high spot is and then just rotate the blade only 180 degrees, if the high spot is still at your marked area then it is the blade not the arbor. Was saw in storage or in use before you pick it up? Old belt's with nylon can take a set and if your shop is cold you may need to run it longer then 10 minutes to warm up. Belts are cheep replace them with a good match set (not from local hardware). Tom

[Wayne Jolly]

OK, I bit the dog and took the saw apart. With no belts on the motor there is still a vibration. I took the motor completely out of the saw and took off the pulley and there is still a slight vibration in the motor. I took the motor apart and everything "looks" ok (including the bearings) but since I have the thing apart I will get some new bearings for the motor and see what gives then.

That brings up two questions.

1. Are there tests that can be run on the motor to make sure it is within "spec"?

2. Is there a Serpentine belt conversion available? I haven't seen one yet.


Thanks again,

Wayne

[Jeffrey Kibler]

Did you ever fix this problem?!?! I'm literally going through the same exact thing right now and getting very frustrated. Any advice you would have would be greatly appreciated. I really don't want to buy a new motor.